Departure from normal maps depict the difference between annual precipitation totals and the
historical "normal". 2011 annual precipitation is compared with the 1981-2010 normal.
2003 through 2010 annual precipitation is compared with the 1971-2000
normal. Years prior to 2003 were compared with the 1961-1990 normal period.

Historical ranking maps depict annual precipitation totals
as they rank when compared to annual totals over the modern record. The values presented are
percentiles. A ranking near zero indicates the year was drier than any found during the period of
record. A ranking near 100 designates that the year was wetter than any found on record. A ranking
of 50 is equivalent to the "median", a measure of central tendency.